Arctic lakes are disappearing as the permafrost beneath them thaws, according to a new study of the impacts of climate warming on the far north. (Courtesy Karen Frey, UCLA)

Arctic Lakes Shrink, Disappear
__________________

INTRO: Lakes and ponds across the Arctic are beginning to shrink, and some have disappeared altogether, as a warmer global climate dries out the northern landscape. Scientists say the loss of surface freshwater across the Arctic portends a dramatic ecological shift that could have long-term impacts on everything from subsistence to weather to ocean circulation.

STORY: Geography professor Laurence Smith from the University of California Los Angeles knew something strange was happening across the Arctic when he noticed Siberian rivers were carrying far more freshwater than usual.

All that freshwater had to be coming from somewhere. To solve the mystery, Smith compared satellite images of nearly 11,000 Siberian lakes in the early 1970s with images taken between 1997 and 2004.

These satellite images of lakes in Siberia taken in 1973 (left) and 1997 (right) show a decline in the size and number of lakes in the region. Click for larger view. (Courtesy Laurence Smith, UCLA)

In all, Smith says 1,170 lakes became smaller, shrinking a total of 359 square miles. And in just 30 years, 125 lakes had completely disappeared, and the lake beds are now covered by vegetation.

Larry Smith compared satellite photos of northern Siberia taken in the 1970s with images taken recently to discover that arctic lakes were drying up as arctic temperatures rise. (Courtesy Larry Smith, UCLA)

SMITH: "In the earth sciences world, this is a very rapid, dynamic change."

Smith, together with scientists from the State University of New York and the University of Alaska Fairbanks, published their research in a recent issue of the journal Science. They say the lakes drained away after the frozen ground beneath them, called permafrost, thawed. UAF researcher Larry Hinzman.

HINZMAN: "Lakes in the southern region of permafrost are relatively thin. They are just lakes perched atop the permafrost, and if the permafrost thaws completely through, then they start to drain."

Interestingly, lakes in northern Siberia actually gained in size. Smith says that's because the permafrost beneath them is thicker and slower to thaw. In time, he says those lakes will shrink as well.

Lakes in Alaska also are shrinking as the underlying permafrost thaws. Researchers have documented lake declines in the Yukon Flats, the Seward Peninsula, and the Copper River region. And studies done two years ago by Canadian scientists found lakes there also have disappeared. Laurence Smith of UCLA says if the trend continues, the arctic landscape will look very different in coming decades.

SMITH: "With the river discharges that we have spoken of and now this
study, the long-term impact is a shift from above-ground storage of water
to below-ground storage of water."

That shift would likely have cascading impacts on wildlife, the environment, the weather, and even Arctic Ocean circulation. Migratory birds, fish, and other wildlife important to Alaska's Native subsistence users likely will be the first to feel the pinch as marshy habitat dries up. And with drier soils, Hinzman says the danger of forest fires will increase.

HINZMAN: "We get around Fairbanks something like 3,000 lightning strikes a day in the summer, but most don't amount to anything. But if we have a lot drier soils, then we are going to see a lot more forest fires and more severe forest fires."

And there may be other impacts—so much freshwater running off the land into the Arctic Ocean could alter the ocean food web, as well as change ocean circulation patterns that drive weather.
Audio version and related websites
(above right)

Arctic Science Journeys is a radio service highlighting science,
culture, and the environment of the circumpolar north. Produced by
the Alaska Sea Grant College Program and the University of Alaska
Fairbanks. The shortcut to our ASJ news home page is
www.asjradio.org.